This invention relate to a stepless infinitely variable transmission (IVT) machine which is capable of producing an output angular velocity which is continuously variable over a predetermined range of angular velocities relative to the input angular velocity.
Many IVT machines have over the years been proposed and developed in attempts to produce, from a constant input angular velocity, an acceptable linear continuously variable output angular velocity and torque.
The basic approach to these machines has been initially to apply a single input angular velocity to a number of parallel stages of the machines which by means of cams, slotted plates, linkages, off-centred sun gears, non-circular gears, orbital devices and so on produce pulsed or cycled angular velocities (angular acceleration and deceleration cycles) which are appropriately phased to the input angular velocity. The pulsed or cycled angular velocities from the machine input stages are then used to drive selective extraction devices, such as overrunning or sprag clutches and/or differentials which extract the maximum portions of the driven cycles of the parallel stages to provide modulated angular velocity outputs. These outputs are then recombined in an output stage of the machine to provide the output angular velocity of the machine. Examples of the these machines are disclosed in the specifications of the following publications: WO 82/02233, WO 89/11604, WO 90/01648, WO 91/18225 and WO 94/11652.
Common problems which are typically associated with IVT machines of the prior art are that:
they are capable of transmitting power in only one direction of rotation, which cannot be reversed,
their cyclic angular velocity generating devices generate, in each parallel stage of the machine, a full cycle of a periodic motion on each revolution of their input shafts with their single drive direction overrunning clutch extraction devices being capable of clipping only the single maximum velocity peak from each cycle. The consequence of this is that the angular velocity output arrangements of the machines, such as planetary gear systems, are largely incapable of fully modulating the coarsely rippled output of the extraction devices to an acceptable purely or nearly so theoretically constant linear output velocity, and
the majority of the cyclic angular velocity generating devices which are employed in the IVT machines and which include oscillating components such as the slotted plates, linkages which drive or are driven by off-centre gears, cams and the like suffer from balancing and other vibration problems which are principally caused mainly by shock loads generated by the direction changing mechanisms.
A method of operating an IVT machine according to the invention includes the steps of rotating an angular velocity input member of the machine at a constant angular velocity applying the input angular velocity in a fixed ratio to two parallel stages of the machine which each include a plurality of cyclic angular velocity generating devices which in each stage are rotated in a common direction, generating a cyclic angular velocity by means of each cyclic angular velocity generating device to produce the same number of angular velocity output cycles from each stage for each revolution of the angular velocity input member with the cyclic angular velocity output of each stage being evenly phased relatively to the other, inverting the cyclic angular velocity outputs of at least one stage relatively to the other, adjusting the amplitudes of the cyclic output angular velocity outputs of the cyclic angular velocity devices in at least one of the stages [18,20] to correspond in amplitude and shape to those of the other stage as the angular velocity ratio of the machine is changed, applying each of the cyclic angular velocities of the cyclic angular velocity generating devices in each stage to an extraction device causing each of the extraction devices to extract the absolute global maximum or minimum angular velocity peak pulses from each of the cyclic angular velocities, summing and combining the pulsed outputs from each stage applying the relatively inverted combined individual pulsed outputs from each stage individually to a planetary gear arrangement cancelling the inverted, equal amplitude, evenly phased pulsed outputs from each stage in the planetary gear arrangement and applying a single non pulsing output angular velocity from the planetary gear arrangement to an output member of the machine.
The cyclic angular velocity generating devices may each include at least two shafts which are coupled by at least one universal joint and the method includes the steps of adjusting the amplitude of the cyclic angular velocity of each cyclic angular velocity generating device by moving one of the shafts relatively to the other to vary their angular dispositions relatively to each other.
An infinitely variable transmission according to the invention comprises an angular velocity input member, an angular velocity output member, two parallel stages of cyclic angular velocity generating devices, a drive arrangement for applying angular velocity from the input member to each of the angular velocity generating devices, extraction devices which are each driven by a cyclic angular velocity generating device in each of the two stages which extracts the absolute maximum angular velocity pulsations from the cyclic angular velocity output of the cyclic angular velocity generating device which drives it, means for varying the amplitude of the cyclic angular velocity produced by at least one of the stages, an arrangement for summing and combining the pulsating angular velocity outputs from the extraction devices and applying a single non-pulsating output angular velocity to the output member, characterised in that each of the cyclic angular velocity generating devices includes two shafts which are coupled to each other by at least one universal joint, the drive means includes a drive arrangement for driving each of the angular velocity generating devices in a first of the stages in a first direction of rotation and each of the angular velocity devices of the second stage in an opposite direction and in a fixed ratio of rotation relatively to the angular velocity generating devices of the first stage so that each stage produces the same number of angular velocity cycles per revolution of the input member and the amplitude varying means is an arrangement for angularly moving one of the shafts of each of the cyclic angular velocity generating devices relatively to the other in at least one stage to enable the amplitudes of the cyclic angular velocities generated by the cyclic angular velocity generating devices in that stage to be varied to correspond to the angular velocity amplitudes in the remaining stage.
The angular velocity generating stage may include at least three cyclic angular velocity generating devices and the angular velocity generating stage two cyclic angular velocity generating devices. Conveniently, the angular velocity generating devices in each stage are rotationally phased 60xc2x0 apart with reference to the input member.
The universal joint sets of the stage 18 may be rotated by the drive means in a ratio of 1:1 relatively to and in the same direction of rotation as the input member and the universal joint sets of the stage are rotated in a ratio of 1:1.5 relatively to and in a direction opposite to the direction of rotation of the input member.
In a preferred form of the invention the angular velocity generating devices are each a universal joint set which includes a universal shaft which carries at each of its ends a universal joint with one of the universal joints being driven by the drive means with the other connected by a shaft to an extraction device. Preferably, the universal shaft of each universal joint set is telescopically variable in length. The yokes of the universal joints of the universal joint sets which are attached to the universal shaft are preferably fixed in each set at 90xc2x0 to each other.
The components of the drive arrangement may be located between and on two circular plates and the components of the transmission are located in a cylindrical housing with the plates of the drive means fixed to the housing wall with the remainder of the components being at least partially rotatable about the housing axis to vary the output amplitudes of the cyclic angular velocities of the universal joint sets by varying the angular disposition of the universal shafts of the universal joint sets relatively to their universal joints.
The extraction devices may be rotatably mounted between two circular plates with the shafts of the universal joint sets passing slidably through the plates and the extraction devices between them. The plates may each be rotatably mounted coaxially in the housing on a guide track on the inner wall of the housing.
The extraction devices may each include a boss with which a shaft of a universal joint set is engaged, opposed clutch plates with one of the clutch plates being engaged with the boss and the other with an output gear with both clutch plates being movable relatively to each other in the axial direction of the shafts between a first position in which they are spaced from each other and a second position in which they are engaged with each other and means for causing movement of the clutch plates between their two positions of movement, in dependence on the angular position of rotation of the shafts with which they are engaged, twice during each revolution of the shafts and for adjustably varying the time period of engagement of the plates to cause their output gear to partially rotate twice during each cycle of rotation of the drive shafts and so to extract an output gear movement pulse from the global absolute maximum and minimum portions of each cycle of rotation of the drive shafts.
The clutch plate movement causing means, in one form of the invention, may be a double lobed cam arrangement and two cam followers which are carried by the extraction device boss and the extraction device includes biasing means biasing the cam followers onto the cam arrangement.
The cam arrangement conveniently includes two annular rings with one concentrically located within the other to be relatively rotatable about and clear of the shaft, two diametrically opposite raised cam lobes which extend over a predetermined limited portion of the circumferential length of and project outwardly from the annular face of each of the rings on a common side of the rings, and a control arm which projects radially outwardly from at least one of the rings for rotating the ring and the lobes on it from a position in which both lobes on the rings overlap and are in radial register to a position in which the two pairs of lobes partially overlap each other to increase the circumferential length of the composite lobes.
The clutch plates are dog-tooth clutch plates and the extraction devices may each include two synchronisation ring plates with plates each being associated with one of the clutch plates and each synchronisation plate includes a ring of radial teeth which face and mesh with those on the opposite synchronisation plate with the synchronisation plates being movable relatively to their associated clutch plates towards and away from the remaining synchronisation plate and means biasing the synchronisation plates away from the faces of the clutch plates so that when the clutch plates are moved towards each other the teeth on the synchronisation plates first engage each other and, if necessary, fractionally rotate relatively to the other to ensure a clean mesh of the dog-teeth on the clutch plates when brought into engagement.
In another form of the invention the clutch plates could be smooth faced metal plates and the extraction devices each include means for electrically magnetising at least one of the plates to cause the plates to become magnetically coupled, and electrical switch means which is synchronised with the shaft for switching electrical current to the clutch plate magnetising means twice for every revolution of the shaft for predetermined time periods during each revolution of the shaft. The clutch plate movement causing means may be an electrical device for moving at least one of the plates towards the other to become coupled and electrical switch means which is synchronised with the shaft for switching electrical current to the clutch plate moving means twice in predetermined time periods during each revolution of the shaft.
The cyclic angular velocity amplitude adjusting means may include a carrier which is engaged with the shafts of the universal joint sets with the carrier including a radially extending control pin and the housing wall a helical guide slot through which the pin projects to be movable from one end of the slot, at which the components of the universal joint sets are in axial alignment and the angular velocity of the universal joint sets is non-cyclic at the low end of the transmission ratio range, to the other end of the slot at which the carrier has rotated the plates to the maximum position of angular displacement of the universal shafts of the universal joint sets to achieve maximum cyclic angular velocity output amplitude at the high end of the transmission ratio range.
Preferably, the housing additionally includes a circumferential slot in its wall through which the ends of the cam arms of the extraction devices project and a suitable control arrangement on the outside of the housing for moving the control pin in its slot and causing concomitant movement of the cam arms to vary the amplitude of the pulsed output angular velocities of the extraction devices to compensate for cyclic angular velocity amplitude changes of the universal joints as the control pin is moved.
The summing arrangement for summing the pulsed outputs of the extraction devices of each of the cyclic angular velocity generating stages may include two gear arrangements which each combine the pulsed angular velocity outputs of the extraction devices of one of the stages to provide two inverted and evenly phased pulsed angular velocity outputs with the pulses in each output angular velocity having the same shape, amplitude. The summing arrangement may include a planetary gear arrangement which drives the infinitely variable transmission output member with the planetary gear arrangement having an e value of xe2x88x921 to which the summing arrangement outputs are separately applied for the planetary gear arrangement to cancel the inverted summing arrangement output pulses and to generate and apply a variable non-pulsating linear output velocity to the output member.